a = -4 (slider from -5 to 5, step 1)
b = 6 (slider from -5 to 10, step 1)
f(x) = x^(2) / 10
n = 16 (slider from 0 to 50, step 1)
O = UpperSum(f, a, b, n)
l: (b - a) / n
U = LowerSum(f, a, b, n)